Feb. 25, 2011 -- Breastfeeding for six months or more may reduce the risk that babies born to diabetic mothers become obese later in life, a new study shows.

"This is perhaps the first study to show that, indeed, if these babies are breastfed as recommended, or more, then their increased risk of obesity is reduced to levels seen in offspring not exposed to diabetes during pregnancy," says study researcher Dana Dabelea, MD, PhD, an epidemiologist and associate professor at the Colorado School of Public Health at the University of Colorado, Denver.

Other experts hailed the study, which is published in Diabetes Care, as well-designed and important.

"I really think they did an excellent job," says Kathleen Marinelli, MD, director of lactation support services at Connecticut Children's Medical Center in Hartford and member of the United States Breastfeeding Committee. "It was very clever the way they defined their breast milk intake or their exclusivity. ... A sticking point in all studies on breastfeeding, is 'How do you define how much breast milk the baby actually got?' And I thought this was very cleverly done and well done."

"They thought they might see a big difference between those babies whose mothers did not have diabetes and those babies whose mothers did have diabetes in terms of obesity protection down the road, depending on how much breast milk they got," says Marinelli, who was not involved in the study. "And if they got more than six months of breast milk, they didn't. And that's actually a good thing, because it shows that you can sort of wipe out that negative potential effect on the baby, if you breastfeed long enough."

And experts say the metabolic benefits of breastfeeding extend to mom, too, by helping her recover from gestational diabetes and protecting her against developing diabetes again later in life.

Maternal Diabetes and Childhood Obesity

In the womb, babies of mothers who have diabetes are exposed to more glucose and free fatty acids than babies whose mothers don't have diabetes.

"So these fetuses are overnourished, even before the babies are born, so that makes them more heavy at birth, but also they have a higher percent of fat mass, not just a higher birth weight at birth," Dabelea tells WebMD.

"Now the interesting question is why do these effects persist over the life course? And here is where we don't quite know everything," Dabelea says, "But one of the proposed mechanisms is that since these offspring are overnourished in utero, this hypernutrition changes their satiety point so they only feel full when they're overfed."

"And they tend to consume increased amounts of food throughout their life because their satiety point has been altered, permanently," she adds.

Breastfeeding Combats Obesity

For the study, Dabelea and her colleagues compared the fat distribution, height, waist measurements, and body mass index (BMI) of 89 children born to diabetic mothers to those of 379 children who had not been exposed to diabetes in utero. The average age of the children in the study was 10.

Mothers were asked about whether they breastfed their babies or used formula. They were also asked how long they breastfed and when they introduced solid foods and other beverages.

Because so many moms mixed breast milk and formula feedings, the researchers developed a sliding scale, between 0 and 1, that they used to statistically weight each child's exposure to breast milk.

The researchers found that among those children who were exposed to diabetes in the womb, those who were breastfed for less than six months had significantly higher BMIs, had thicker waists, and stored more fat around their midsections compared to children who were breastfed for more than six months.

What's more, when they compared children who were exposed to diabetes to those who weren't, they only saw significant differences in those who were breastfed for less than six months. The groups looked nearly the same when they were breastfed for six months or more, indicating that the disadvantage conveyed by being exposed to diabetes had been wiped out.

Breastfeeding May Protect Mother and Infant

"What we wanted to do was look at what we would consider a high-risk group and to see if breastfeeding had an impact on obesity in that setting," says study researcher Stephen Daniels, MD, PhD, pediatrician-in-chief at Children's Hospital in Denver. "And what we found, in fact, is that breastfeeding does seem to be protective."

"Certainly all women should be breastfeeding, but women who have diabetes and who have babies that are exposed to diabetes in utero should be especially aware that breastfeeding could have an important benefit to their child over time," Daniels tells WebMD.

And other research suggests that the benefits may extend to mom, as well.

"If a mother has gestational diabetes and she nurses her baby, she lowers her risk for developing diabetes down the road," Marinelli says. "Real diabetes, not just diabetes during the pregnancy, so that's her benefit. If she breastfeeds her baby, she lowers her baby's risk for becoming obese. And she lowers her baby's risk for not only becoming obese, but for developing diabetes, because there is a genetic component to diabetes so if you're born to a parent who has diabetes, you are at risk for getting diabetes. But if you're breastfed, that risk is lowered."

The important thing to remember, Marinelli notes, is that the benefits appear to be related to how long a mom continues; the American Academy of Pediatrics recommends that women breastfeed for six months or longer after their babies are born.